During a study of publications having possible relation to the present invention, the inventor has become aware of the following prior U.S. patents:
______________________________________ Patentee Patent No. Issue Date ______________________________________ Benbow et al. 1,178,208 April 4, 1916 Gardner 2,749,941 June 12, 1956 Tobias 3,700,004 Oct. 17, 1972 Andis 3,754,574 Aug. 28, 1973 Bonney 3,774,504 Nov. 27, 1973 ______________________________________
The present invention was made by the latter patentee, Bonney, while seeking to provide a valve with no internal channeling in either the spool or body, eliminating complicated castings and machining, for a valve that can be made smaller than comparable sliding spool valves, that operates easier than a sliding spool valve and which provides zero leakage without a need for the close spool tolerance needed in sliding spool valves that do not have ball checks.